JP4942738B2 - Production of Cu / Zn / Al catalyst via formate ester - Google Patents

Description

Detailed Description of the Invention

  The present invention relates to a method for producing a Cu / Zn / Al catalyst, a catalyst that can be produced by the method, and a method for applying the catalyst in methanol synthesis and reforming of methanol and low temperature maintenance of carbon monoxide.

Cu / Zn / Al catalysts that catalyze the conversion of CO, CO ₂ and H ₂ to methanol have been known for some time. Although the molecular ratio of copper to zinc can be varied in the known catalyst, generally more copper is present. Further, some of the zinc component can be replaced by calcium, magnesium, and / or manganese. Aluminum oxide used as a temperature stabilizing material can be partially replaced by chromium oxide.

  For example, DE 1965007 describes a catalyst for the synthesis of low temperature methanol. In order to produce the catalyst, the basic carbonate is precipitated from an appropriate zinc and copper salt solution by addition of alkali metal carbonate. This is separated from the aqueous phase, dried and sintered to produce the appropriate oxide. The zinc and copper oxides are then mixed with aluminum oxide to produce an oxide suspension that does not contain more than 20% solids. It is further homogenized, where the homogenization is carried out until the diffused oxide does not settle for 2 hours. After homogenization, the mixture is dried, tableted and sintered. In order to convert the oxide form to a catalyst, it is further reduced in a hydrogen stream.

  German Offenlegungsschrift 2302658 A describes catalyst precursors that can be used for methanol synthesis. In order to produce the catalyst precursor, first, a precipitate containing a divalent metal such as zinc and a trivalent metal such as aluminum in the form of a compound that can be decomposed into an appropriate oxide by heat is generated. Suitable compounds are for example carbonates or bicarbonates. Furthermore, the 2nd deposit containing the copper compound which can be decomposed | disassembled into an oxide with a heat | fever is produced | generated. Mix both precipitates. This is followed by typical drying and sintering steps to produce an oxide from the metal compound and possibly promote the formation of a spinel structure. Subsequently, the solid is made into a tablet. In order to convert the precursor to an active catalyst, the tablet form is reduced in a stream of hydrogen.

German Offenlegungsschrift 2056612A describes a process for the production of methanol in which the conversion is carried out over a catalyst containing zinc, copper and aluminum. The catalyst has the chemical formula:
(Cu _x Zn _y ) Al ₂ (OH) ₁₆ × CO ₃ × 4H ₂ O
Where x and y are numerical values of 0.5 to 5.5 and the sum of x and y is 6. The mixed crystal compound is precipitated by adding an alkali carbonate, an alkali bicarbonate, or a mixture thereof to an aqueous solution containing copper, zinc, and aluminum salts. The molecular ratio of the sum of the divalent metals copper and zinc in the mixed crystal system to the trivalent aluminum is constant and is 6: 2. For the production process, copper, zinc and aluminum are dissolved in water in the form of suitable salts, in particular nitrates, and in proportions depending on the required catalyst composition. The solution is heated to a temperature of 50 to 100 ° C., in particular 70 to 100 ° C., and treated with an aqueous precipitant solution, for example an alkali carbonate solution, with the temperature adjusted appropriately. The precipitate formed is filtered, washed and dried. The dried compound is sintered at a temperature of 200 to 500 ° C. for 12 to 24 hours. The sintered product is formed into a tablet and then converted to the active state of the catalyst by reduction in a hydrogen stream.

  U.S. Pat. No. 4,279,781 describes a catalyst for the synthesis of methanol comprising copper and zinc oxide and a metal oxide for temperature stabilization such as, for example, aluminum oxide. The ratio of copper oxide to zinc oxide is 2: 1 to 3.5: 1 calculated by metal weight. The preparation of the catalyst is carried out by precipitating together soluble zinc, copper, aluminum salts, such as their nitrates. Thereby, complete mixing of the catalyst components is achieved. The catalyst precursor is reduced in a hydrogen stream to make it active.

  From European Patent Application No. 025689A2 a catalyst for the synthesis of methanol is known which contains copper oxide and oxide salts as catalytic substances and aluminum oxide as temperature stabilizing substance. This catalyst is characterized by a specific pore radius distribution, wherein the proportion of pores having a diameter of 20 to 75 Å (angstroms) (interpores) is at least 20%, more than 75 （(macropores) The ratio of the pores having the diameter of 80% at maximum. This required pore radius distribution can be achieved by using colloidally distributed aluminum oxide or aluminum hydroxide in the production of the catalyst. In order to produce this catalyst, the catalytic copper oxide-zinc oxide component is mixed with colloidally distributed aluminum oxide, for example, from a solution of an appropriate salt such as nitrate, sulfate, hydrochloride, acetate or the like. Precipitation with an alkali-reactive substance in the presence of aluminum hydroxide. The precipitated product is then dried and sintered, compressed into a shaped body, and reduced if necessary.

According to EP 0152809 A2, containing copper oxide and zinc oxide in the form of an oxidative precursor and converting them into catalytic components by reducing at least part of the copper oxide There are also known catalysts for synthesizing alcohol mixtures containing methanol and higher alcohols, which contain aluminum oxide as temperature stabilizing substance and at least one alkali carbonate or alkali oxide. Said oxidizing precursor has pores having a diameter of 14 to 7.5 nm in a proportion of 20 to 70% of the total pore volume. The alkaline component is an alkali metal of 13 to 130 × 10 ⁻⁶ gram atoms per gram of oxidizing precursor. The aluminum oxide component is obtained from colloidally distributed aluminum hydroxide. To prepare the catalyst, a copper and zinc nitrate solution is generally used, preferably a precipitation with an aqueous K ₂ CO ₃ solution. The concentration of the solution is preferably 5 to 20% by weight. Instead of starting with nitrate, it is also possible to start with the appropriate metal formate or acetate. Precipitation can also be performed using potassium bicarbonate. The precipitation can be carried out at any time or continuously. The precipitation is preferably carried out by continuously mixing a colloidally distributed copper oxide and zinc nitrate solution containing aluminum oxide with an aqueous solution of K ₂ CO ₃ . After precipitation, the washed catalyst precipitate is sintered and alkalized by treatment with a solution of an alkali metal compound. The alkalized catalyst precursor is dried and then pressed into a molded body in a known manner, and an anti-tacking agent such as graphite can be added. In order to convert the catalyst precursor to the active form, it is reduced in a stream of hydrogen.

  From WO 03/053569 a catalyst for methanol synthesis is known which contains copper oxide and zinc oxide as catalytic agents and aluminum oxide as temperature stabilizing material. In order to produce a catalyst, a required hydrocarbon salt or hydroxide is precipitated from a solution containing Cu and Zn salt and a part of Al salt by an alkali carbonate or alkali aluminate solution. Either a Cu and Zn salt solution or an alkali carbonate or alkali aluminate solution contains an aluminum hydroxide sol. The resulting precipitate is separated from the precipitation solution, washed, dried and sintered if necessary. The preparation of the catalyst is preferably carried out from copper nitrate or zinc nitrate, which are preferably precipitated with sodium carbonate or sodium aluminate.

  Japanese Patent Application Laid-Open No. 2001-14479 describes a copper-zinc catalyst for the reaction of carbon monoxide and water to carbon dioxide and water. The catalyst comprises a solution containing copper formate and zinc formate. Produced by mixing with an aqueous solution of an alkaline substance. The resulting precipitate is then filtered, washed, dried and sintered. The sintered solid component is wetted by adding water and applied to the surface of the honeycomb-shaped support. An aluminum oxide sol or zirconium oxide sol can be used as the binder. These are added during wetting of the sintered precipitate. Accordingly, the aluminum oxide is not evenly distributed in the catalyst and is disposed only between the catalyst particles. That is, it acts only as a binder between the catalyst particles containing copper and zinc and between the honeycomb support and does not become an active component of the catalyst.

  In order to produce a Cu / Zn / Al catalyst for the synthesis of methanol, copper nitrate and zinc nitrate are mostly used in technically practical processes due to their water solubility. Accordingly, waste water containing a large amount of sodium nitrate is generated during precipitation. If this is allowed to flow into the river, it will lead to excessive eutrophication. Therefore, it is necessary to drastically reduce the content of water-soluble nitrogen in the wastewater generated during the production of the methanol synthesis catalyst before flowing into the ground river.

  Accordingly, an object of the present invention is to provide a catalyst for synthesizing methanol which, on the one hand, enables a significant reduction of salt components, particularly alkali metal nitrates, on the one hand, and on the other hand a catalyst activity which is at least equivalent to that of a catalyst produced from metal nitrates. It is to provide a method for producing a Cu / Zn / Al catalyst.

  The object is solved by a method having the features of claim 1. The subject of the dependent claims is a preferred additional embodiment of the method.

  In the method for producing a Cu / Zn / Al catalyst according to the present invention, a first aqueous solution containing at least copper formate and zinc formate is first generated. Further, a second solution containing a precipitant is produced. As used herein, a precipitant is understood to be a reagent that directly or indirectly produces ions, such as hydroxide ions and / or carbonate ions, by which metals, in particular copper, zinc, and aluminum can be precipitated. . Said first and / or second solution comprises an aluminum hydroxide sol / gel mixture. Here, the aluminum hydroxide sol is understood to be a finely diffused distribution of aluminum hydroxide in water, in which polyvalent acids are already formed by the condensation of aluminum hydroxide, but in the aqueous phase. However, the particles cannot be recognized with the naked eye, that is, it is assumed to be a transparent liquid. An aluminum hydroxide gel is a solution of aluminum hydroxide in water that has already formed large aggregates of polyvalent acids and can be recognized by the naked eye, for example, as turbidity in an aqueous phase. It is understood to be diffusion.

  In the precipitation step, the first solution and the second solution are purified, whereby a precipitate is obtained. The precipitate is separated from the aqueous phase, where the aqueous phase becomes waste water, which is directed to a reprocessing step.

  The precipitate is washed until it has an alkali content of less than 500 ppm for a catalyst dried at 600 ° C. Subsequently, the precipitate is dried, sintered if necessary, and pulverized.

  In the method according to the present invention, waste water containing nitrate is not generated. By using copper formate and zinc formate as water-soluble copper and zinc salts, the wastewater contains formate ions that can be reprocessed in a simple manner. By using formate, contamination of wastewater by organic components is suppressed to a relatively low level. This is an advantage over the use of higher carboxylic acids such as acetic acid, which increases organic contamination in the wastewater by a greater number of C—H bonds. Yet another advantage is that the formic acid used to produce copper formate and zinc formate can be produced at low cost, and therefore the method according to the present invention is also cost effective.

  For the process according to the invention it is important that at least part of the aluminum is added in the form of an aluminum hydroxide sol and the rest in the form of an aluminum hydroxide gel in the precipitation solution. Omitting the addition of the aluminum hydroxide sol / gel mixture into the metal salt solution reduces the weight-time-yield (GZA, [methanol kg / {catalyst kg × time}]).

  The precipitate is separated and carefully washed so that the alkali content is reduced to less than 500 ppm, in particular less than 400 ppm, particularly preferably in the range from 100 to 300 ppm, for an oxidation catalyst ignited at 600 ° C. The cleaning liquid generated at that time can be integrated with the waste liquid containing formic acid and regenerated as necessary. After washing, drying, and optionally sintering, the oxidized form of the catalyst still has a residual formic acid content of less than 5% by weight, in particular 0.5 to 4% by weight, particularly preferably 1 to 2% by weight. It will be a thing. The formic acid content can be determined, for example, by oxidation titration or quantitative chromatographic methods such as HPLC.

  In addition to copper formate and zinc formate, the first aqueous solution can contain calcium, magnesium, manganese, cerium, lanthanum, and other accelerators such as ruthenium or palladium. Other accelerators can be used alongside the accelerators described above. It is also suitable for the accelerator to be added in the form of formate as well, especially in the first aqueous solution. Their proportion in the oxidized catalyst is preferably less than 10% by weight, in particular less than 5% by weight, calculated as oxide. When noble metals such as ruthenium or palladium are used as promoters, they are preferably included in an amount of less than 1% by weight.

  As described above, in the method according to the present invention, the first and / or second solution comprises an aluminum hydroxide sol / gel mixture. As a raw material product of aluminum hydroxide sol / gel, for example, a commercially available product can be used. However, an aluminum hydroxide sol / gel mixture can also be produced by adding some ammonium hydroxide to a diluted aluminum salt solution, in which case conversion to a coarsely diffused hydroxide derivative is achieved. Avoid temperature rise to delay. According to another variation, a small amount of acid can be added to the alkali aluminate solution, thereby forming an aluminum hydroxide sol / gel. The aluminum hydroxide sol / gel is preferably included in the first aqueous solution. The resulting product produced from the aluminum hydroxide sol / gel functions as both a carrier and a temperature stabilizing material. Although not limited to that theory, the inventors have formed a three-dimensional network when the aluminum hydroxide sol / gel mixture is heated, and belong to the active chemical species in the gap and exist after reduction. We expect copper crystallites to be placed. Thereby, further growth of copper crystallites during methanol synthesis is suppressed, thereby increasing the stability of the catalyst and its service life during the processing process.

  Zinc oxide firstly has an important influence on the formation of active chemical species, while its partially needle-shaped structure contributes to the stabilization of the catalyst. In addition, zinc oxide acts as a poison-binding agent by reacting with existing sulfur compounds.

  Calcium, magnesium, manganese, cerium, and lanthanum oxides, which are optionally included as promoters, also provide a stabilizing effect.

The first solution containing a mixture of various metal salts is:
-An aqueous copper formate solution is produced by dissolving the copper salt free of residues by the addition of formic acid;
-Producing an aqueous diffusion solution or solution of zinc salt;
-Producing an aqueous aluminum salt solution;
-Integrating said copper formate solution, zinc salt diffusion solution or solution, and aluminum salt solution;
It is preferable to generate by.

  If the Cu / Zn / Al catalyst needs to be further modified by a promoter, it can be added, for example, into the first solution. The promoter can be added in the form of an appropriate salt such as carbonate, oxide salt, or hydroxide salt. The salts can be added at any time, ie to the copper formate solution, to the zinc salt diffusion solution or solution, or after the copper formate solution and zinc salt diffusion solution or solution are combined. can do. In particular, an expensive accelerator such as a precious metal is preferably added in a later processing step. For example, a powder which is added to a suspension before spray drying or finely dispersed after spray drying and dried. Can be sprayed on top.

  In the preparation of the copper formate-zinc solution, the formic acid is at least 10 mol%, in particular 10 to 20 mol%, particularly preferably 14 to 16 mol, based on the amount of copper and zinc salt used in consideration of the stoichiometry. It is preferred to add the formic acid in such an amount that it is present in excess of mol%. It is preferred that the pH value of the copper formate solution be less than 3, especially less than 2.5 after the addition of formic acid.

  In a preferred method embodiment, a zinc salt solution or diffusion solution is integrated with the copper formate solution. After integration of the copper formate solution and zinc salt solution or diffusion solution, both copper and zinc are present in the solution in the form of formate. The solution obtained has a pH value of 3.0 to 4.0, in particular 3.5 to 3.7. Subsequently, the aluminum salt solution is added to the copper / zinc solution.

  The aluminum salt solution is preferably added to the copper / zinc solution as a plurality of divided portions. In this case, at least the first part of the aluminum salt is prepared in such a way that at least the first part of the aluminum salt is dissolved in water with the addition of formic acid.

  In the production of the first portion of the aluminum salt solution, for example, sodium nitrate is first dissolved in water and then the formic acid is adjusted so that the pH value is less than 5, particularly 4.5 to 2, particularly preferably 4 to 3. It is preferable to carry out the method by adding. It is preferred to add formic acid until a clear solution is obtained.

  The second portion of the aluminum salt solution is preferably made by dissolving the second portion of the aluminum salt in water. At that time, no formic acid is added to the second portion of the aluminum salt solution. In order to complete a first solution that contains all metal salts prior to precipitation, the first portion of the aluminum salt solution and the second portion of the aluminum salt solution are shifted in time into an aqueous copper / zinc solution. It is preferable to add.

The second portion of the aluminum salt solution is made, for example, by dissolving NaAlO ₂ in water. The pH value of the aqueous NaAlO ₂ solution ranges from 11 to 14, in particular from 12 to 13, depending on the alkali excess of the extract.

  The ratio of the parts of the first and second aluminum salt solution is 0: 100 to 100: 0, in particular 1:99 to 99: 1, more preferably 30:70 to 70:30, in particular with respect to the aluminum content. Preferably it can be selected at about 50:50.

  The production of the aluminum salt solution is preferably carried out at a temperature below 40 ° C., in particular below 30 ° C. This temperature is not allowed to exceed when the aluminum salt solution is added to a copper / zinc solution, a copper formate solution, or a zinc salt solution or a diffusion solution. By this method, formation of the polymerizable aluminum compound diffused coarsely is suppressed. The coarsely diffused polymerizable aluminum compound is understood to be an aluminum hydroxide compound having particles that are visible to the naked eye and settle relatively quickly. Therefore, it is preferable to carry out the production in a container equipped with an appropriate cooling device.

Aluminum salts that can be suitably used in the process according to the invention are, for example, aluminum diformate or triformate, Al (NO ₃ ) ₃ hydroxide, or NaAlO ₂ . The aluminum salt solution preferably has an aluminum concentration in the range of about 0.4 to about 1.1 mol / l, especially about 0.9 to 1.1 mol / l. Here, the upper limit of the range is determined by the solubility limit of the aluminum salt, while the lower limit is calculated for economic reasons.

For copper salts, the anions are oxides, hydroxides and carbonates, or derivatives thereof obtained by reduction, and are independent as distinguishable elements in the first solution or in the oxidized form of the catalyst. It is preferred to use a salt, which can no longer be confirmed. The copper salt is preferably selected from CuO, Cu (OH) ₂ and Cu (OH) ₂ × CuCO ₃ .

  Selecting a zinc compound, also as a zinc salt, whose anion is no longer harmful in the first solution or the precursor material of the oxidized form of the catalyst, and preferably no longer identifiable as an identifiable element Is preferred. It is preferred to use ZnO as the zinc salt.

  The concentration of the copper formate solution is such that the copper concentration ranges from about 0.1 to about 0.5, in particular from about 0.3 to about 0.5 mol / l after the copper formate solution and the zinc salt solution or diffusion solution are combined. It is preferable to select so as to be. In this case, the upper limit is determined by the solubility limit of the copper salt, while the lower limit is determined for economic reasons, which results in a larger volume due to the reprocessing of the diluted solution, whereby the process according to the invention is carried out. This is because the design size of the apparatus to be implemented is affected.

  The zinc salt concentration is about 0.1 to about 0.2 mol / l, particularly about 0.15 to about 0.2 mol / l after the integration of the copper formate solution and the zinc salt solution or diffusion solution. It is preferable to select the range. Again, the upper limit is determined by the solubility limit of the zinc salt and the lower limit is determined for economic reasons.

  The aluminum salt solution is preferably added to the copper / zinc solution. Preferably, the pH value of the first solution containing the total amount of Cu, Zn and Al is set in the range of 4.0 to 5.0, particularly 4.2 to 4.4.

  As the precipitating agent, it is preferable to use an alkali metal group. As the alkali metal group, it is preferable to use an alkali metal carbonate, an alkali metal hydrogen carbonate, or an alkali metal aluminate. It is preferred to use sodium as the alkali metal. For example, when soda solution is used as a precipitating agent, it is preferred that the soda solution has a concentration of 80 g / l to 200 g / l, especially 170 to 180 g / l.

  According to another embodiment of the method according to the invention, hydrogen peroxide is used as the precipitating agent. The hydrogen peroxide is added to the first solution or diffusion solution containing copper, zinc, and aluminum in the form of its formate or its hydroxyformate. This hydrogen peroxide oxidizes the formate to carbonate, thus precipitating the metal in the form of its bicarbonate, carbonate, or hydroxide. During the oxidation of formate, first, bicarbonate and then carbonate are formed with increasing pH. The metal ions used are separated as hydroxy carbonate in the order of Al-Cu-Zn in the precipitation order. Therefore, the use of an alkaline solution containing carbonate can be omitted. Along with hydrogen peroxide, other suitable oxidants such as ozone can also be used.

  In order to produce an oxidized precatalyst material, the first and second solutions are first combined, whereby a precipitate is obtained. The precipitation is carried out in such a way that during the precipitation the pH value is kept in the range 3.5 to 7.5, in particular 6.0 to 7.0, particularly preferably 6.5 ± 0.1. Is preferred.

  It is preferred to keep the temperature in the range from 25 to 95 ° C., in particular from 50 to 75 ° C. during the precipitation.

  It is preferred to age the precipitate formed after mixing. Therefore, the suspension obtained when mixing the first and second solutions can be transferred into, for example, an aging container, and the suspension can be stirred therein using, for example, an appropriate stirring device.

  This aging is preferably carried out with a duration of 10 minutes to 10 hours, in particular 1 to 5 hours.

  It is preferred to adjust the temperature of the suspension during aging, where aging is preferably carried out in the temperature range above 60 ° C., in particular from 65 to 80 ° C.

  The integration of the first and second solutions is preferably performed in such a way that each solution is guided into the mixing vessel in parallel and mixed there. In that, rapid mixing is implemented, for example using a suitable stirring apparatus.

  However, it is preferred that the precipitation is carried out as a continuous precipitation. Therefore, an appropriately sized mixing container is provided, in which the first and second solutions are continuously injected, and the resulting mixture is continuously discharged. The volume of the mixing vessel is such that the first and second solutions can be continuously injected into the mixing vessel and the mixture can be continuously discharged, with the residence time of the mixture being between 0.1 seconds and 10 seconds. It is preferred to select a range of minutes, in particular 1 to 120 seconds, particularly preferably 1 to 20 seconds.

  The residence time of the mixture in the mixing vessel is highly dependent on the size and flow rate of the mixing vessel. Those skilled in the art can appropriately set the dimensions of the mixing vessel and the inflow and outflow rates of the solution or suspension.

After precipitation and, if necessary, an aging step, the precipitate can be separated from the aqueous phase, for which a general method such as filtration can be used. The precipitate is then washed and dried. The precipitate is preferably sintered after drying. Depending on the method used, the sintering is carried out at a temperature of 140 ° C. to 1000 ° C., in particular 170 ° C. to 350 ° C., and at least 0.1 second, in particular at least 4 minutes, more preferably 20 minutes to 8 hours, particularly preferred. Is preferably carried out for a duration of 30 minutes to 4 hours. Depending on the chosen sintering conditions, the formate remaining in the filter cake is largely extinguished by oxidation in the air or intramolecular redox reaction in an inert gas during sintering. In the latter case, Cu (HCO ₂ ) ₂ × H ₂ O is usually first decomposed into H ₂ and CuC ₂ O ₂ . Copper oxalate is then further converted to CO ₂ and elemental copper. Sintering can be carried out in a common apparatus. In industrial production, either a pulsatile reactor or a fluidized bed reactor such as a rotary tube reactor widely used commercially can be used because of its good heat change. The pulsating dryer allows for very short drying times in less than 1 second, typically in the range of 0.1 seconds to 4 minutes, where very high temperatures up to 1000 ° C. can be used.

The sintered powder can be crushed as necessary and then processed into a tablet shape or an extrudate by a general tool. However, it is also possible to wet the powder and grind it to very fine particles, and to coat the resulting suspension on a suitable support, for example a honeycomb member. Here, a general method can be used. Therefore, the particle size is appropriately adjusted so that the average particle size D ₅₀ is 10 nm to 10 μm, particularly 100 nm to 5 μm. The average particle size can be determined by, for example, a laser beam diffraction method. Suitable catalysts can be produced, for example, having a particle size such that their D ₅₀ value is in the range of 2 to 3 μm.

  The main advantage of the method according to the present invention is that wastewater containing formate formed after separating the precipitate can be reprocessed by relatively simple means. Therefore, the waste water containing formate is subjected to oxidation treatment, and at that time, formate ions in the aqueous solution are substantially oxidized into carbonate, hydrogen carbonate, carbon dioxide, and water according to the pH value. For example, the content of formate in wastewater such as sodium formate is usually 0.2 to 1.5 mol / l, in particular 0.8 to 1.0 mol / l in the industrial conversion step of the process according to the invention. It is possible that higher or lower formate concentrations may be present. By oxidation of the wastewater, the formate concentration is reduced to a value in the range of less than 0.1 mol / l, in particular 0.01 to less than 0.075 mol / l, particularly preferably 0.02 to 0.04 mol / l. Can be reduced. This corresponds to a reduction of more than 95% of the amount of formate contained in the wastewater.

  According to a preferred embodiment, hydrogen peroxide is added to the wastewater containing formate for the oxidation treatment. The hydrogen peroxide is preferably added in the form of a solution to the wastewater containing formate, and the hydrogen peroxide concentration is preferably in the range of about 9 to 20 mol / l (up to about 60% by weight). The concentration of the hydrogen peroxide solution used can be increased to more than 90% by weight if the prescribed transport rules have to be followed. It is preferable that hydrogen peroxide is added in excess, and the amount added is selected in the range of 160 to 200 mol%, particularly 160 to 170 mol% with respect to the formate contained in the wastewater. Is preferred. Along with hydrogen peroxide, other oxidants such as ozone or sodium hypochlorite can also be used. In selecting an oxidant, for example, manufacturing costs as well as costs related to environmental regulations play an important role. Depending on the legal limits as well as the cleaning steps that can be used thereafter, it is sometimes not necessary to oxidize the entire amount of formate. It may be sufficient if the concentration of formate is significantly reduced by chemical oxidation treatment and the wastewater so treated is transferred to a biological purification process, for example, if necessary.

  Treatment of wastewater containing formate using hydrogen peroxide can be carried out at a temperature of 20 to 95 ° C., in particular 50 to 80 ° C., and in a pH range of 4 to 8, in particular 5.0 to 6.5. Is preferred.

  According to one embodiment of the method according to the invention, the oxidation treatment of wastewater containing formate is already carried out before the separation of the precipitate. Therefore, after the ripening step, for example, an appropriate amount of hydrogen peroxide is added to the suspension, and the precipitate can be separated only after the formate ions are sufficiently oxidatively decomposed. On the other hand, hydrogen peroxide can be added to a formate solution that already contains Cu, Zn, and Al in the course of time, where the precipitating agent, or carbonate ion, oxidizes the formate ion. Manufactured.

  For example, the oxidation treatment of wastewater by adding an appropriate oxidizing agent such as hydrogen peroxide can be carried out very simply in terms of equipment, and also enables treatment of wastewater having a relatively high formate ion concentration. However, it is also possible to carry out the oxidation treatment only by biological treatment of wastewater containing formate. If necessary, wastewater containing formate can be diluted to an appropriate concentration.

  The oxidation treatment of wastewater containing formate is preferably performed in such a manner that the formate concentration in the wastewater is less than 0.1% by weight after the oxidation treatment.

  When comparing a Cu / Zn / Al catalyst produced using formate with a catalyst produced from nitrate, the catalyst produced by the method according to the present invention has at least equal or better activity. It shows both equivalent selectivity. The long-term stability of the catalyst produced using formate, as determined by a methanol synthesis test at 250 ° C., is also at least equivalent to or somewhat better than the stability of the catalyst made from metal nitrate It becomes. Therefore, the subject of the present invention is also a catalyst that can be produced by the above-described method.

  The catalyst according to the invention contains in its oxidized form less than 5% by weight, especially 0.5 to 4% by weight, particularly preferably 1 to 2% by weight of formate, calculated as formic acid. The formate structure can be retained by sintering so as not to impose a fracture burden, which can play an important role in achieving high activity in the key lock principle that often occurs in catalysts. Sintering that is not subject to a fracture burden performed at about 170 ° C. for 4 minutes produces a catalyst with very high activity at a temperature of 250 ° C.

The catalyst according to the present invention is characterized by having a high pore volume. The ratio of the interstitial pores having a radius of 3.75 to 7.0 nm to the total pore volume is preferably more than 30%, in particular 30 to 80%. The total pore volume consists of the volume of pores having a radius of 3.75 to 7500 nm. This pore volume can be measured by the mercury penetration method. Preferably, the total pore volume is 100 mm ³ / g to 700 mm ³ / g, in particular 250 mm ³ / g to 450 mm ³ / g in a 6 × 4 mm tablet form.

  The ratio of copper calculated as CuO with respect to the weight of the oxidation catalyst molded body corresponds to the loss on ignition at 600 ° C., and is preferably selected from 55 to 69% by weight, particularly 60 to 63% by weight.

  The ratio of zinc calculated as ZnO with respect to the weight of the oxidation catalyst molded body corresponds to the loss on ignition at 600 ° C., and is preferably selected from 20 to 33% by weight, particularly 25 to 31% by weight.

The proportion of aluminum calculated as Al ₂ O _{3 with} respect to the weight of the oxidation catalyst compact is preferably selected from 5 to 20% by weight, in particular from 8 to 11% by weight.

  The percentage values for copper, zinc and aluminum relate to a catalyst which has been ignited at 600 ° C. for 3 hours.

  The catalyst according to the invention has, in oxidized form, an alkali ion content, in particular sodium ions, of less than 500 ppm, in particular less than 300 ppm, particularly preferably from 100 ppm to 300 ppm.

The catalyst according to the present invention is ^90m 2 / g than in its oxidized form, it is preferred in particular having a specific surface area of 100 m ² / g greater.

  The catalyst according to the present invention can be processed into a molded body having an arbitrary shape. For example, it can be formed into a ring shape, a shaped body with 3 to 20 holes, a tablet shape with a smooth or corrugated surface, or a honeycomb shape. The dimensions of the molded body are the same as general numerical values. In order to produce a molded body, a powdered catalyst is formed into a tablet shape of 6 × 4 mm, for example, while adding an anti-sticking agent such as graphite as necessary to form the molded body.

The catalyst is converted from the oxidized form to the active form before use. Therefore, copper oxide is at least partially reduced to elemental copper. Therefore, it is preferable to reduce the oxidized form of the catalyst according to the present invention in a hydrogen stream. This activation can be carried out directly in the synthesis reactor, and is first carried out in such a manner that it is reduced using an inert gas containing a small amount of hydrogen, such as nitrogen. The nitrogen usually contain 2.0% by volume of _{H 2.} This raises the temperature from 100 ° C. to 235 ° C. over 16 hours. The hydrogen content is then increased, for example 20% by volume of H ₂ (the rest N ₂ ) is reduced in the temperature range of 235 to 270 ° C. over 3 hours. The reduction finish is carried out with 99.9% H ₂ for about 3 hours and at a temperature of 270 ° C. to 300 ° C. Usually activated by a space velocity of 3000 to 4000 l of reducing gas per hour and per liter of catalyst.

  In the reduced state, the size of the copper crystallite is preferably about 4 to 12 nm, particularly 5 to 7 nm.

The catalyst according to the invention is particularly suitable for use in methanol synthesis. The subject of the present invention is therefore also a method of applying the catalyst described above to the synthesis of methanol from CO, CO ₂ and H ₂ . The synthesis is usually from about 200 to 320 ° C., in particular from 210 to 280 ° C., from about 40 to 150 bar, in particular from about 60 to 100 bar, and from about 2000 to 22000, in particular from 8000 to 12000 l per hour and per liter of catalyst. It is preferred to carry out at a gas space velocity, in which the synthesis gas is about 5 to 25, in particular 6 to 12% by volume CO, about 4 to 10% by volume CO ₂ and about 10 to 30% by volume. N ₂ + CH ₄ (inert gas) and the balance H ₂ can be included.

The catalyst according to the present invention is further suitable for use in methanol reforming and carbon monoxide low temperature maintenance. The latter is still a reaction referred to as low temperature transformation (LTS) as a temperature in the range of about 175 to 250 ° C., in particular 205 to 215 ° C. and a steam / gas ratio in the range of about 0.4 to 1.5 (Nl / Nl). Implemented in Typical feed gas mixtures, and CO of about 3 volume%, and 17 volume% of CO _2, 2 and volume% of _{N 2,} 78 comprise a volume% of _{H 2,} it is a catalyst 1l per well per hour Are introduced into the reactor at a space velocity of about 2000 to 12000 l of dry gas (ie anhydrous). A good catalyst achieves 70-85% CO treatment at a space velocity of 11200 h ⁻¹ and a steam-gas ratio of about 1.5.

  The invention will now be described in more detail with reference to examples.

Example (a) Formation of a copper solution 5.054 g Cu (OH) ₂ × CuCO ₃ (Cu—content: 27.7 wt%, equivalent to 1400 g Cu) was diffused in a 10 l beaker to generate CO ₂ A total of 2399 ml of 85% formic acid (D = 1.1856 g / cm ³ ) is divided and mixed until the end of the process. The copper solution has a pH value of 2.35 and a temperature of 55 ° C.

(B) Formation of Cu / Zn solution (previous stage of the first solution) A ZnO diffusion liquid is generated from 781 g ZnO and 4000 ml H ₂ O in a 5 l beaker. The suspension is combined with the copper solution obtained in (a) above. Add 890 ml formic acid and 33.6 l non-mineral water in portions while further diffusing. Stir the solution that is blue and initially milky until completely clear.

(C) Production of sodium carbonate solution (second solution) 24000 ml of Na ₂ CO ₃ solution having a concentration of about 180 g CO ₃ per 100 ml is produced and the solution is heated to 70 ° C.

(D) Formation of aluminum solution I 2193 ml of demineralized water is placed in a 5 l-stirring device equipped with cooling means, and 246.7 g of NaAlO ₂ is added. The solution is temperature adjusted to a maximum of 30 ° C., after which 350 ml of formic acid is added in portions. The milky solution has a pH value of about 4.0.

(E) Production of aluminum solution II 2193 ml of water is placed in a stirrer equipped with cooling means, and 246.7 g of NaAlO ₂ is added in portions. At this time, care should be taken that the temperature of the solution does not exceed 30 ° C. The solution is stirred until a completely clear solution is obtained.

(F) The solution obtained by precipitation (b) is transferred into the first auxiliary tank of the mixing device. Subsequently, the aluminum solution I obtained in (d) is poured into the tank, where it is stirred at room temperature until the integrated solution is completely clear. If necessary, water can be added to eliminate turbid elements of the solution. The solution is heated to 70 ° C. before precipitation begins. About 30 minutes before the start of precipitation, the aluminum solution II obtained in (e) is transferred into the tank, whereby an emulsion-like white-blue suspension is formed.

The second preliminary tank is filled with the Na ₂ CO ₃ solution obtained in (c) and heated to 70 ° C.

  The solutions contained in the first and second tanks are simultaneously fed into the mixing device and reach the overflow vessel from there after a residence time of about 20 seconds. The pump speed at that time is set so that the pH value is about 6.5 ± 0.1 during precipitation. The mixture reaches the overflow vessel from the mixing device. The suspension obtained from the overflow vessel reaches the aging vessel where it is maintained at about 65 ° C. with stirring. Precipitation is complete after 35 minutes. Thereafter, the apparatus is washed with about 600 ml of demineralized water, and the temperature in the aging container is raised to 70 ° C. After completion of the washing step, the suspension is aged with stirring. The start of aging is defined by the end of the cleaning process. The aging time applied in the examples is shown in Table 2.

  After completion of aging, the suspension is filtered, washed with demineralized water until the sodium residue in the filter cake is reduced to less than 350 ppm, and the resulting solid component is sprayed in a reverse flow using a single material nozzle. Dry by drying. A suspension with a dry substance content of 30% by weight is set as the inflow. The heating gas inflow temperature is 330 to 350 ° C., and the product outflow temperature is 110 to 120 ° C. The dried powder is then stored in a porcelain petri dish and sintered at about 320 ° C. for 50 minutes in a shelf-type kiln or a laboratory rotary kiln operating in stages.

(G) Treatment of waste water Waste water generated during filtration and washing is treated by adding hydrogen peroxide, and at that time, the pH value of the waste water is maintained at 5 to 6.5 with sulfuric acid, and the temperature is maintained at about 70 ° C. . In this case, the formate concentration of the wastewater is adjusted to a value of 2.8 wt% to 0.09 wt%. The selectivity defined by the converted formate molar value of the hydrogen peroxide used is about 60%.

Comparative Example (a) Production of copper / zinc-nitrate 781.25 g of zinc oxide is added to a 9.79 kg copper nitrate solution containing 1400 g of copper. Then 2077 g of nitric acid (58%) is added and the mixture is stirred until the solids are completely dissolved.

(B) Formation of aluminum nitrate solution Dissolve 246.7 g of Na ₂ AlO ₂ in 1.5 l of fully desalted water. Then 1365 g nitric acid (58%) is added and stirred until a clear solution is obtained. The resulting aluminum nitrate solution is added to the copper / zinc-nitrate solution and the resulting Cu / Zn / Al solution is heated to 60 ° C.

(C) Formation of aluminum sol 246.7 g of Na ₂ AlO ₂ is dissolved in 1.5 l of completely desalted water with stirring for 30 minutes. The resulting solution is added to the Cu / Zn / Al solution and the mixture is heated to 60 ° C.

(D) The mixture obtained in (c) is poured into the first preliminary tank of the precipitation mixing apparatus. The second reserve tank of the mixing procedure is filled with 25 l of an aqueous solution containing 172 g Na ₂ CO ₃ per liter. Both solutions are simultaneously pumped into the mixing vessel and the mixture is guided from there to the aging vessel.

  After completion of the precipitation, the mixing vessel is washed with completely demineralized water, the temperature in the aging vessel is raised to 70 ° C., and the precipitate is aged for 1 or 4 hours. After completion of aging, the suspension is filtered, washed with demineralized water until the sodium residue in the filter cake is reduced to less than 350 ppm, and the resulting solid component is sprayed in a reverse flow using a single material nozzle. Dry by drying. The heating gas inflow temperature is 330 to 350 ° C., and the product outflow temperature is 110 to 120 ° C. The dried powder is then stored in a porcelain petri dish and sintered at about 320 ° C. for 50 minutes in a shelf-type kiln or a laboratory rotary kiln operating in stages.

  Examples of precipitation carried out and the sintering conditions used in the following are listed in Tables 2a and 2b. Similarly, in the table, the chemical composition and physical parameters of the obtained oxidation catalyst pre-stage material are described.

The determination of physical parameters is performed in the following way:
Measurement of Cu crystallite dimensions:
The measurement of the dimensions of the Cu crystallite is performed by X-ray diffraction (XRD). Cu (111) reflection is measured in the range up to 43.3 ° (2θ). The half bandwidth of reflection and the integrated intensity are calculated by a pseudo-Forked function. The Cu crystallite dimensions are calculated using Scherrer's equation based on the calculated half bandwidth.

In preparation for crystallite size x-ray image determination, the oxidation catalyst is reduced as follows:
2 to 5 g of tablet-shaped body having dimensions of 6 × 4 mm are heated from room temperature to the maximum temperature in a tubular reactor with a reducing gas (98% N ₂ , 2% H ₂ ) at a heating rate of 2 ° C./min. . The catalyst produced from the formate is heated to a maximum temperature of 80-120 ° C. The catalyst produced using nitrate is heated to 175 ° C. overnight. Within 2 hours thereafter, a) the catalyst via formate / carbonate is adjusted to 180 ° C .; b) the catalyst via nitrate / carbonate is adjusted to a maximum temperature of 240 ° C. Thereafter, while maintaining the maximum temperature, the hydrogen content of the reducing gas is increased to 100% within 1 hour, and then the sample is further reduced for 3 hours.

Measurement of specific surface area The BET specific surface area is determined according to DIN 66132 for a powdered oxidation catalyst and a 6 × 4 mm tablet type by the nitrogen one-point method.

Measurement of loss on ignition When it is necessary to measure loss on ignition in a tablet mold, it is first crushed into a powder. The sample to be measured is weighed and contained in a weighed porcelain container, which was previously heated in a muffle kiln at 600 ° C. for 3 hours and then cooled to room temperature in a dehydrator. The vessel is heated to 600 ° C. for 3 hours in a muffle kiln and subsequently cooled to room temperature in a dehydrator. The cooled container is weighed again, and the ignition loss at 600 ° C. is calculated from the difference.

Measurement of lateral pressure strength The lateral pressure strength is measured according to DIN EN1094-5, 1995 09 edition, fire-resistant products for cut-off-Volume 5: "Measurement of low-temperature pressure strength of molded products". This measurement is carried out according to the manufacturer's instructions, for example with a commercially available device such as Schleuniger 6-D or Elveca TBH310MD.

  For 100 tablets, which is a general number of samples, the pressure applied to the cylindrical shell during the destructive experiment is measured, and the average value, standard deviation, and minimum and maximum hardness are determined by a total program specific to the device. . The distribution of tablet mold material hardness (N) is shown in graph form.

Measurement of the pore volume The pore volume is determined for the powdered oxidation catalyst as well as for the 6 × 4 mm tablet shaped body by the mercury penetration method according to DIN 66133.

About 10-20 g of the sintered catalyst powder is mixed in 25 + xml H ₂ SO ₄ (25%) in a 300 ml Erlenmeyer flask and dissolved while heating to about 70 ° C. This amount of xml of H ₂ SO ₄ (25%) is calculated by the minimum amount of sulfuric acid that is additionally required in order to completely dissolve the metered dose. Fill to about 100 ml with distilled water. The solution is adjusted to a pH value of 8 to 10 by adding about 2.5 to 25 ml NaOH (30%). The solution is heated to 70 ° C. for at least another 5 minutes. Then 20 ml of KMnO ₄ solution (0.2N) is added and the solution is heated to boil gently for at least 30 minutes. The hot solution is oxidized with H ₂ SO ₄ (25-50 ml) and 20 ml of oxalic acid (0.2N) is added, thereby reducing manganese dioxide and excess KMnO ₄ to Mn ²⁺ . The added succinic acid solution must correspond exactly to the oxidizing equivalent of the permanganic acid solution in the inclusion of reducing equivalents. The final clear solution is titrated with 0.2N KMnO ₄ until a mild redness is observed.

Calculation:
Each 1 ml of 0.2 N KMnO ₄ used corresponds to 4.5 mg formate. The percent calculated formate content of the sample is:
[% Formic acid salt] = [(KMnO ₄ solution 0.2N shown in 4.5mg of formate salt / ml) × 100 (KMnO ₄ solution already used 0.2N shown in ml) ×) / mg The amount of sample weighed in)

  This method yields a reliable result with an error rate of less than + 8% at 0.08 to 0.5% by weight for the formate concentration in the solution to be titrated. This error rate can be reduced to ± 2% by using a 0.02N permanganate solution. Since the accuracy of the method depends on the formate concentration, the metered dose is initially adapted to the expected value, and after the initial results are obtained, the formate in the above range for the solution to be titrated Perform the titration again with a metered dose adjusted appropriately to yield a concentration.

  The formate contents of the samples of Examples 3 and 5 are listed in Table 1.

  The physical properties of the catalyst produced are listed in Table 2. Here, Table 2a relates to a powdered catalyst, while the values in Table 2b relate to a catalyst press-molded into a 6 × 4 mm tablet.

Methanol activity test Oxidized tablet-shaped molded product is divided into 4 parts, and 2.5 to 3.5 mm sieving portion is filled into a tubular reactor, and after activation, the standardized activity test is periodically changed. Was carried out under the following temperature. During the evaluation, the weight-time-yield (GZA) is determined as an average value for each low temperature interval in kg (methanol) / (kg (catalyst) × h). In a test furnace system consisting of 6 to 16 individual tubes, a catalyst C79-7 manufactured by Sued Chemie in Munich, Germany was used as a reference in one test tube, and was determined for other samples. Each GZA is compared to a standard value. This method has the advantage that slight changes in the synthesis gas composition are equal for all samples, so that the results from different test times can be compared with each other.

  By-products are measured using gas chromatographic tests on concentrated samples, each with an internal standard. The numerical values obtained are likewise described in comparison with standard ones.

  The results of the methanol activity test are listed in Table 3.

Claims (28)

-Producing a first aqueous solution comprising at least copper formate and zinc formate;
-Producing a second aqueous solution containing a precipitating agent;
The first solution and / or the second solution comprises an aluminum hydroxide sol / gel mixture;
-Mixing said first solution and second solution in a precipitation step, wherein a precipitate is formed;
-Separating the precipitate from the aqueous phase forming the wastewater;
Washing the precipitate until the alkali content corresponding to the catalyst dried at 600 ° C. at high temperature is less than 500 ppm,
-The precipitate is then dried, and the first solution further comprises:
-An aqueous copper formate solution is produced by dissolving the copper salt so that there is no residue by addition of formic acid;
-Producing an aqueous diffusion solution or solution of zinc salt;
-Producing an aqueous aluminum salt solution;
A method for producing a Cu / Zn / Al catalyst, characterized in that the Cu / Zn / Al catalyst is produced by integrating the copper formate solution and zinc salt diffusion solution or the solution and the aluminum salt solution.   The process according to claim 1, wherein the pH value of the copper formate solution is less than 3.   A solution or diffusion solution of zinc salt is integrated with a copper formate solution to form a copper / zinc solution, wherein the obtained copper / zinc solution has a pH value of 3.0 to 4.0, and an aluminum salt solution A process according to claim 1 or 2, comprising adding to the copper / zinc solution.   The aluminum salt solution is added as a plurality of divided solutions, wherein at least a first portion of the aluminum salt solution is produced by dissolving in water with formic acid added to at least a first portion of the aluminum salt. The method described.   A second portion of the aluminum salt solution is generated by dissolving a second portion of the aluminum salt in water, and the first portion of the aluminum salt solution and the aluminum solution of the aluminum solution to form the first solution. The method according to claim 3 or 4, wherein a second portion is added to the copper / zinc solution.   Heating the aqueous solution of the aluminum salt, the first portion of the aluminum salt solution and / or the second portion of the aluminum salt solution to a temperature of up to 40 ° C. before precipitation. The method according to any one of claims 1 to 5.   7. A process according to claim 1, wherein the pH value is maintained in the range of 3.5 to 7.5 during the precipitation step. Copper salts CuO, Cu _{(OH) 2,} and Cu _(OH) A method according to any one of claims 1 to 7, characterized in that selected from 2 · CuCO _3.   9. The method according to claim 1, wherein ZnO is selected as the zinc salt.   The method according to any one of claims 1 to 9, wherein the precipitating agent is alkali-based.   The method according to claim 1, wherein the precipitating agent is hydrogen peroxide.   The method according to any one of claims 1 to 11, wherein the precipitate is aged after the precipitation.   The method according to claim 12, wherein the aging is carried out with a duration of 10 minutes to 10 hours. The method of claim 12 or 13, wherein aging is characterized by performing at a temperature range of 60 ° C. greater.   The method according to claim 1, wherein the precipitation step is carried out as continuous precipitation.   The method according to any one of claims 1 to 15, wherein the first solution contains copper and zinc in a ratio selected from 1:99 to 99: 1.   The method according to any one of claims 1 to 16, wherein the precipitate is sintered after drying.   The method of claim 17, wherein the precipitate is sintered at 140-1000 ° C and for a duration of at least 0.1 seconds.   The wastewater contains formate, and the wastewater containing formate is subjected to an oxidation treatment, and at that time, formate ions are substantially oxidized to carbonate, bicarbonate, carbon dioxide, and water. The method according to any one of claims 1 to 18.   20. The method according to claim 19, wherein hydrogen peroxide is added to waste water containing formate for the oxidation treatment.   21. The method according to claim 19, wherein the oxidation treatment of the wastewater containing formate is performed before the separation of the precipitate. A catalyst for the synthesis of methanol produced by the process according to any of claims 1 to 21 and having a formate content of less than 5% by weight relative to the oxidation catalyst. The catalyst according to claim 22 , for the synthesis of methanol , characterized in that the proportion of interpores having a radius of 3.75 to 7.0 nm to the total pore volume is greater than 30%. 24. A catalyst according to claim 22 or 23 for methanol synthesis, characterized in that the proportion of copper, calculated as copper oxide, relative to the weight of the oxidation catalyst compact is selected from 55 to 69% by weight. Calculated as zinc oxide, the catalyst according to any one of 24 the preceding claims 22 for the methanol synthesis, which comprises selecting the ratio of zinc to the weight of the oxidation catalyst molded bodies 20 to 33 wt%. Calculated as aluminum oxide, the catalyst according to any one of claims 22 for the methanol synthesis, which comprises selecting the ratio of aluminum to the weight of the oxidation catalyst molded bodies from 5 20% by weight 25. The catalyst according to any one of the oxidized catalyst claims 22 for the methanol synthesis, characterized by having an alkali ion content of less than 500 ppm 26.   28. A method of applying a catalyst according to any of claims 22 to 27 for methanol synthesis.